Soap bars for cleansing are typically prepared by saponifying (neutralizing) triglyceride/fatty acids. In this saponification process, various fats (e.g., tallow, palms and coconut oil blends) are saponified in the presence of alkali (typically NaOH) to yield alkaline salts of fatty acids (derived from the fatty acid chains forming the glyceride) and glycerol. Glycerol is then typically extracted with brine to yield dilute fatty acid soap solution containing soap and aqueous phase (e.g., 70% soap and 30% aqueous phase).
The soap solution is then typically dried (e.g. to about 15% water) and the remaining mass is typically mixed, milled, plodded, cut and stamped into bars. Alternatively, the soap solution can be cast into moulds, blisters, etc.
The chain length of fatty acid soaps found in the final bar varies depending on the starting fat or oil feedstock (for purposes of this specification, “oil” and “fat” are used interchangeably, except where context demands otherwise). Longer chain fatty acid soaps (e.g., C18 palmitic or C18 stearic) are typically obtained from tallow and palm oils, and shorter chain soaps (e.g., C12 lauric) may typically be obtained from, for example, coconut oil or palm kernel oil. The fatty acid soaps produced may also be saturated or unsaturated (e.g., oleic acid).
Typically, longer molecular weight fatty acid soaps (e.g., C14 to C22 soaps) are insoluble and do not readily generate foam, despite the fact that they can help making the foam generated by other soluble soaps creamier and more stable. Conversely shorter molecular weight soaps (e.g., C8 to C12) and oleic acid chain length soaps lather quickly. However, the longer chain soaps (typically saturated, although they may also contain some level of unsaturated such as oleic) are desirable in that they help maintain the structure of the bar and do not dissolve as readily. Unsaturated soaps (e.g., oleic) are soluble and contribute to a denser, creamier foam, like the longer chained soaps.
Since, as noted, all the fats are added, saponified and dried at the beginning of the process, saponification of both long and short chain length materials occurs together and the final soaps are distributed homogeneously throughout the final bar product after finishing. No concentrated regions of specific chain length soaps are made when varying chain length soaps are saponified together.
Typically, skin benefit agents, which will form part of the final bar, may be added together with the fats during saponification or during drying stages (where temperatures are very high, for example, above 100° C.). However when these ingredients are added in specific product variants, they are normally added during mixing (at lower temperatures) to avoid complexity in the factories. The benefit agents are normally liquids, pastes or soft particle and can adequately be added at this later stage. Addition of benefit agents (e.g., silicones; humectants such as glycerol or sorbitol; emollients, such as isopropyl palmitate) during saponification/drying ensures they are thoroughly and homogeneously mixed. This is true even for benefit agents which have relatively high melting points (e.g., greater than 50° C., typically greater than 60° C.). Such benefit agents can readily mix at temperatures typically used for saponification (90 to 120° C.), and heat and efficient mixing ensure full homogenization and homogeneous incorporation of benefit agent throughout the final soap matrix.
As noted, some benefit agents (which we refer to as “finishing adjuvant materials”) can be and are typically added after saponification and drying, and just before soap noodles (e.g., soap noodles comprising benefit agents which are added at the saponification stage) are mixed, milled, plodded, etc. Typically, this second type of benefit agent are those that improve the aesthetic quality of the bar, especially the visual, tactile and olfactory properties, either directly (perfume) or indirectly (preservatives).
Examples of adjuvants (both “non-finishing” materials which may be added at saponification, or “finishing” materials which may be added after saponification and at the mixing stage) include but are not limited to: perfumes; opacifying agents such as fatty alcohols, ethoxylated fatty acids, solid esters, and TiO2; dyes and pigments; pearlizing agent such as TiO2 coated micas and other interference pigments; plate like mirror particles such as organic glitters; sensates such as menthol and ginger; preservatives such as dimethyloldimethylhydantoin (Glydant XL 1000), parabens, sorbic acid and the like; antioxidants such as, for example, butylated hydroxytoluene (BHT); chelating agents such as salts of ethylene diamine tetra acetic acid (EDTA) and trisodium etridronate; emulsion stabilizers; auxiliary thickeners; buffering agents; and mixtures thereof.
Adjuvants are typically added at a level of between about 0.1% to about 3%, preferably between 0.1% and 0.5% and most preferably between about 0.2 to about 0.4% based on the total weight of the bar composition. As noted above, different adjuvants may be added at or after saponification.
As indicated, many adjuvant materials/benefit agents have relatively low melting points (lower than 50° C.). By contrast, soaps produced during the saponification process (typically made with C16Na+/C18Na+/C18:1 Na+) typically have melting points above 100° C. Thus, these materials will not melt during the post-saponification finishing stages when finishing adjuvants are typically added.
Unexpectedly, applicants have now found that if, rather than saponifying all fat materials (comprising mixture of all chain lengths) in a one-step process, fats in which 75% or greater of the chain lengths available for saponification and/or neutralization are C14 or longer are saponified separately (in a different stream) from fats in which 75% or greater of the chain lengths available for saponification and/or neutralization are C12 or less, tremendous benefits are achieved.
Specifically, one stream will produce soaps in which 75% or more by wt. of the soap molecules produced are C14 or greater, and one will produce soaps in which 75% or more by wt. of the soap molecules produced are C12 and less. Because the soaps are made at a different stage in the process, the two types of soap may be combined and mixed later at much lower temperatures. As a result, the soap blends are not homogenized and instead form concentrated regions or domains (the term “regions” and “domains” are used interchangably) of predominantly short chain soap interspersed in a matrix of predominantly long chain soaps which regions are better able to deliver foam. Although mixing time can certainly be longer, mixing time is typically from 1 to 15 minutes, preferably from 2 to 10 minutes. Separate saponification before the two blends are combined also permits different counterions to be used during the different saponification reaction in each stream, if desired.
Further, benefit agents with typically lower melting points than those used in the “main stream” previously noted (typically “finishing” adjuvants), and which normally would be homogenized and dispersed throughout the final bar during a typical one-step saponification process, can be added when the two soaps (formed in separate saponification steps) are mixed at the lower temperature. Since these finishing adjuvants are added at a lower temperature part of the process when two soaps are combined, they will tend to stay in the non-homogenized regions defined by the lower-chain soaps formed with which they will be interacting. Because the lower chain soaps are concentrated in separate regions, they generate much better foam (quantity and quality) upon bar use. Further, because the lower chain soaps solubilize more quickly on rinse, the benefit agents which are entrapped in the region also can be more readily delivered.
Although benefit agents can be added during saponification or post saponification (at lower temperatures) of either stream, the step at which the soaps are combined (at much lower temperature) allows incorporation of low melting point benefit agent into the regions which will form when the soaps are combined and bars are formed. However, selection of benefit agents with specific melting points can still be important. If the melting point of the agents is too low, when the two soaps are mixed, the benefit agents may homogenize even at the relatively low mixing step temperature, and the agents may not stay in the regions for delivery (e.g., they may migrate and interact with main bar matrix); if the melting point is too high, they may stay in the regions, but they may also remain gritty and not provide performance benefits. In general, it is preferred that lower melting point benefit agent be added to the saponification stream where short chain soaps are being made, but after the saponification (when temperature is lower) and before the two streams are mixed, or that they be added when both soaps are combined.
Typically, we have found that, when benefit agents are added at a temperature of about 30 to 50° C., preferably 25 to 45° C., more preferably 38 to 42° C., the benefit agent (whether added post saponification and during formation of short chain soap; or after the two streams are mixed) tends to remain with the soaps forming the concentrated regions and to also provide desired performance benefits (e.g., they are not too gritty).
The performance of low-chain soap regions can be further enhanced by the ability to select counterions used for saponification. Further, different performance benefits may be achieved in theory by separate addition (at lower temperature stages) of solid, separately made, non-soap detergents.
U.S. Pat. No. 6,730,642 to Aronson et al. disclose extruded multiphase bars in which there is a separately prepared discontinuous phase which is harder than a continuous phase. However, there is no difference disclosed in the composition of the chain lengths of both phases and no disclosure or suggestion that there be a second saponification using predominantly shorter chain fats and done at a different stage than the first saponification. There is no disclosure of mixing the two streams at a defined lower temperature range. Further, the separate phases are mixed for aesthetic purposes only. There is certainly no recognition that lather or other benefits can be delivered when concentrated regions of predominantly low chain-length soaps are formed.
No reference of which applicants are aware disclose soap bars having a main bar matrix comprising predominantly long chain soap and separate regions or domains comprising predominantly low chain length soap. No reference discloses a process for making such bars, or the benefits resulting from such bar. Further, no reference discloses the selection of benefit agents (preferably added during formation of low chain soaps; and/or in a separate stream at the times the low chain soaps and high chain soap are mixed) having defined melting point ranges (e.g., 30 to 45° C.) such that, as indicated, when the benefit agents are mixed at the lower temperatures, they will remain with soaps forming the concentrated domains, yet remain sufficiently non-gritty as to provide benefits.
An accompanying application is directed to compositions having concentrated regions as defined above and the subject application case is directed to the process of making said composition.